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Abstract

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Mid-IR absorption cross-sections are measured for methane, ethane, ethylene and methanol over 2800–3400 cm−1
(2.9–3.6 μm) spectral region. Measurements are carried out using a
Fourier-Transform-Infrared (FTIR) spectrometer with temperatures ranging
296–1100 K and pressures near atmospheric. As temperature increases,
the peak cross-sections decrease but the wings of the bands increase as
higher rotational lines appear. Integrated band intensity is also
calculated over the measured spectral region and is found to be a very
weak function of temperature. The absorption cross-sections of the
relatively small fuels studied here show dependence on the bath gas.
This effect is investigated by studying the variation of absorption
cross-sections at 3.392 μm using a HeNe laser in mixtures of fuel and
nitrogen, argon, or helium. Mixtures of fuel with He have the highest
value of absorption cross-sections followed by Ar and N2.
Molecules with narrow absorption lines, such as methane and methanol,
show strong dependence on bath gas than molecules with relatively
broader absorption features i.e. ethane and ethylene.